Here's what you should do if you wake up before your alarm and don't want to feel tired all day

Many of us start the morning with the sound of an alarm. Yet
there's always that occasional day when you wake up an hour or
two before that classic ringing sound fills the room.

On mornings like this, you've got two choices: Either emerge from
the covers and get a head start to the day, or you try to go back
to sleep.

But which is the better choice if you want to avoid feeling tired
and groggy all day?

That's the question we asked Mayo Clinic professor of medicine
and former president of the American Academy of Sleep
Medicine Timothy
Morgenthaler, MD.

Morgenthaler, who's also board certified in the field of sleep
medicine, says before you choose you should first ask yourself an
obvious, yet key, question: "Am I done sleeping?"

An easy way to answer this question is to determine whether
you've put in enough hours of sleep. Most adults need between
seven and eight hours of sleep a day, and there's no way of
getting around that, according to the National Institute of
Health.

If you've clocked in enough shut-eye, then waking up early is
simply your body's natural reaction to two interacting systems
that control "the overall drive to sleep or stay asleep," said
Morgenthaler:

The first is called sleep
homeostasis, a basic principal that pushes you to sleep
longer and more intensely if and when you haven't slept enough.

The second is your circadian rhythm, or your internal
biological clock, which is responsible for why we start to feel
tired in the evening, as opposed to the morning or afternoon.

While the homeostatic mechanism in your body regulates the
intensity of your sleep, your circadian clock regulates the time
of day your body starts and stops craving sleep.

So if you occasionally wake up early after putting in at least
seven hours of sleep the night before, it's probably your body's
way of telling you that you've satisfied both systems and you
should get up and start your day, Morgenthaler said.

"The overall best is if you can wake up naturally because you’re
done sleeping," he said.

On the other hand, if you're waking up early on just a few hours
of sleep, you should probably try and squeeze in some more
shuteye.

If you get up early, you're not only depriving yourself of sleep,
but you're also robbing your body of the majority of REM (rapid
eye movement) sleep — the stage of sleep that, according to the
National Sleep Foundation:

Provides energy to brain and body

Supports daytime performance

Is when the brain is active and dreams occur

In general, many of us get the most of our REM sleep between
the hours of
3 a.m. and 7 a.m. So if you're waking up early between those
hours and you haven't had at least seven hours of shut-eye, you
might begin to feel groggy as the day pushes on.

Bottom line: If you're like most adults, then you need at least
seven hours of sleep a night — regardless of when you first wake
up.